The present invention relates to a femoral rasp for preparing an intramedullary canal for receiving the stem of a femoral hip prosthesis.
Hip arthroplasty procedure includes anesthesia and patient placement on a table in proper orientation. The patient's body is then stabilized, scrubbed, prepared and draped. Appropriate soft tissue is excised and/or divided for exposure and dislocation of the hip. After the femoral head is dislocated from its associated acetabulum, the head is rotated for better exposure. A femoral neck osteotomy is then performed wherein the head and neck are cut away from the femur shaft. Next, the intramedullary canal is prepared to accommodate the hip stem component of the prosthesis and, ultimately, the stem is anchored within the intramedullary canal.
Preparation of the intramedullary canal is an important step in the overall procedure since the fit between the stem and its associated femur is determined by the size of the prepared cavity. An improper fit of the stem within the cavity often causes rotation of the stem relative to the femur and improper articulation of the hip joint prosthesis.
Hence, the characteristics of the spacing or interface between the exterior surface of the femoral stem and the interior contour of the prepared cavity in the intramedullary canal play an important role in properly anchoring the femoral prosthesis to the femur. A stem of sufficient length has long been recognized as desirable since it provides increased resistance to rotation. However, long stems require large intramedullary cavities, particularly at the calcar leading into the canal, since the overall surface thereof makes it impossible for the insert to pass into the cavity without a significantly oversized entranceway. Such cavities formed by prior art implements produce large gaps or voids between the outside surface of the inserted stem and the inside surface of the cavity. Heretofore, a glove fit between a femoral stem and the intramedullary cavity together with superior anchoring of the stem and resistance to rotation have been considered difficult to achieve.